I 



ON FOSSIL POLYZOA. 25 i 



Terebellaria, Lamouroux. 



' A fossil, dendroid polypary, composed of cylindrical scattered 

 branches, spirally twisted from left to right, or from right to left in- 

 differently; pores prominent almost tubular, numerous, disposed quin- 

 cnncially, and more or less inclined according to their position with the 

 spires.' 



Lamouroux says the genus should be placed after the Millepores and 

 before the Spiroporce, remarking ' that the Spiroporre have the cells or the 

 pores projecting as in Terebellaria, but that this character is observable . 

 only in well-preserved specimens. When the prominent part of the spire 

 has been worn by attrition, it looks like a narrow riband wound round 

 the branch.' 



Two species are described by the author, T. ramosissima and T. 

 antilopa, from the Terrain a polypes at Caen. 



Hagenow's description is the same, but he includes in the genua 

 Ceriopora spiralis, Goldfuss. 



D'Orbigny adopts the genus of Lamouroux with the following 

 character: — 



' Colony entirely fixed by the base, whence spring thick cylindrical 

 dichotomous branches, often very numerous, and forming a dendroid 

 growth. Each branch presents three parallel spiral zones, which begin 

 at th*e end of the branch in a projection formed exclusively of the germs 

 of cells.' He enumerates four species — T. gracilis, D'Orb.; T. antilopa, 

 Lamx.; T. ramosissima, Lamx.; and T. tenuis, D'Orb. 



The peculiar habits of the species are remarkable. Haime says, 

 ' The (colonial) development proceeds by layers of testules (cells), which 

 superpose themselves by following a spiral line, and they increase after- 

 wards downwards, covering themselves more and more.' In the figs. 

 of pi. vi. typical features of the species ai-e given, but the very peculiar 

 spiral habit of T. ramosissima shown in transverse section, and the 

 checked winding habit of T. antilopa, shown in longitudinal section, 

 which will be further alluded to, may be seen in the figures of Lamou- 

 roux, of which Mr. Busk has furnished me with tracings. 



The fossils which ordinarily pass for species of Terehellaria in the 

 cabinets of collectors are a very curious group that may be more closely 

 studied. My own studies are made fi'om specimens from the Cornbrash, 

 and Bradford Clay of Bradford and Stanton, Wilts, and it is from this 

 locality that the School of Mines specimens were obtained. 



To properly master the details of colonial growth, it will be necessary 

 to isolate a single colony. The one furnished by Haime as a specimen of 

 a young colony on stone shows a tapering pi'oximal point, gradually 

 widening by the addition of cells, till a certain fanlike shape is arrived 

 at. A similar growth to this is found in young colonies of Diastopora. 

 If superficially examined it will be seen that the cells are peculiarly 

 arranged, beautifully punctured, with an orifice sometimes circular, at 

 other times semi-circular, and sometimes the cell characters of portions 

 of the colony bear a resemblance to Bidiastopora ramosissima of D'Or- 

 bigny. A complete and critical examination of the type will show that 

 any fragment of stone or shell is sufficient to form the nucleus of a colony. 

 It begins with a primary cell and then enlarges in a spiral direction, but 

 to what extent the riband-like growth would be carried without a check 



